The present invention relates to a computer and function architecture for operating an electrical power-assisted steering system, wherein the control unit has a computer architecture comprising a redundant core, referred to as a dual-core processor.
When using a microcomputer to compute and control the steering assistance function of an electrical power steering system, faults in the computer core must be detected and, in the event of a fault, the system must be shut down since reliable computation and control can no longer be ensured, According to the prior art, a fault in the arithmetic core of the microcomputer is verified by way of double computation of the steering assistance function. The computational algorithms required for this purpose are designed to be diverse. If the results of a control path (Level 1) differ from the diverse monitoring path (Level 2), a fault is assumed to exist in the arithmetic core. Subsequent to a detected difference, the system must be shut down as quickly as possible and thereby transferred into a safe state. However, shutting down the steering assistance function is associated with major limitations for the driver in terms of comfort. Typical output variables include a setpoint value specification for the assistance torque of the servo-motor, however depending on the scope of functions, these may also include the output of steering-internal variables, such as the steering angle information for partner control units.